1. Field of the Invention
The present invention relates to a magnetic disk drive and a servo processing method in the same. More particularly, the invention relates to a magnetic disk drive and a servo processing method, in which an appropriate control operation is performed even when a thermal asperity occurs in an MR head.
2. Description of the Related Art
Generally, there has been utilized a hard disk drive (HDD), or, a magnetic disk drive, as a storage device for a desk-top type personal computer or a notebook type portable computer. This magnetic disk drive records and reproduces data in and from a storage medium (disk) by using a magnetic head. The storage medium is manufactured by coating and depositing a magnetic recording film on a disk-like aluminum substrate (alumina processed).
In recent years, in such a magnetic disk drive, an MR (Magnetoresistive) head is used to record data at a high density on small-diameter disk. The MR head makes use of MR effect provided by a thin permalloy film made of iron and nickel, whose electric resistance changes when an ambient magnetic field changes in intensity.
In the MR head, however, a typical phenomenon called a thermal asperity (TA) may occur. That is, the electric resistance may change due to heat produced by friction when the MR head comes into contact with irregular portions on the disk or dusts. The thermal asperity results in various inconvenience produced in the conventional magnetic disk drive.
If thermal asperity occurs in a servo area storing information necessary for positioning the MR head in a predetermined location on the disk, accurate information indicating the position of the MR head would not be obtained, making it impossible to perform data reproducing. This is particularly true in the case of the conventional magnetic disk drive in which recording and reproducing of data are prohibited when an error occurs in its servo area. In such a magnetic disk drive, data may not be recorded or reproduced in or from a sector in which an error due to a thermal asperity has been detected.